Hydraulic fracturing is a technique for improving production from hydrocarbon reservoirs (e.g., oil and/or gas reservoirs). Hydraulic fracturing entails injecting a liquid into a reservoir so as to create new fractures in the reservoir. In cases where hydrocarbons can move more freely along such fractures than within solid reservoir rock, hydraulic fracture can significantly improve reservoir production.
Accordingly, methods of measuring, predicting and/or controlling hydraulic fracture are of great interest, and have been investigated for some time. For example, in U.S. Pat. No. 7,111,681, detailed mathematical modeling of fracture propagation is considered. In U.S. Pat. No. 4,744,245, in-situ measurements of stress orientation are performed to assist in predicting fracture direction. In U.S. Pat. No. 6,985,816, measurements of microseismic events are employed to determine orientation of fractures resulting from hydraulic fracturing treatment.
In U.S. Pat. No. 7,165,616, separate fracture wells and production wells are operated in a coordinated manner to provide control of hydraulic fracture direction. In U.S. Pat. No. 5,386,875, perforations are formed along a plane of expected fracture formation to provide improved control of fracture direction. In U.S. Pat. No. 5,355,724, a slot is formed in a rock formation undergoing hydraulic fracture to improve control of hydraulic fracture. In U.S. Pat. No. 5,482,116, a deviated wellbore in a direction parallel to a desired fracture direction is employed to provide improved control of hydraulic fracture direction.
However, it remains difficult to understand and/or predict hydraulic fracture direction in cases where reservoir depletion affects reservoir stresses.
Accordingly, it would be an advance in the art to provide a simple method of predicting hydraulic fracture direction in depleted reservoirs.